The number of battery powered electronic devices and gadgets used in daily life is steadily increasing. Important such devices include:
Communications handsets: mobile phones, cordless phones
Infotainement: Music (MP3) players (diskman, ipod, etc.), Mobile TV, portable audio
broadcast receivers
Photo/video: Digi/video cams
Wireless peripherals: Bluetooth headsets, cordless microphones, etc.
Time & navigation: wrist watches/computers, GPS devices
IT: PADs, Laptops, cordless keyboards & mice, etc.
Household: Electronic clocks, thermometer, weather stations, pocket calculators, etc.
Medical: hearing aids, cardiac pacemakers, etc.                Sport: stopwatches, avalanche beacons, bike computers, bike lamps, pocket lamps,pulse monitors, etc.        
Wireless communications has brought certain freedom from wires for the communication. However, recharging of those devices still requires wires. Many other electronic devices use non rechargeable batteries requiring frequent replacement producing an environmental burden. To make matters worse, there is no true standard charging interface. Many different re-chargeable devices require their own wall charger.
Battery technologies have improved, but Personal Electronic Devices (PEDs) in average are getting more power-hungry due to added features and increased usage (e.g. mobile phone with integrated digicam, colour screen, gaming and MP3 players), thus effectively resulting in reduced instead of expanded autonomy time.
Getting power to portable devices has been the focus of a series of recent products that attempt to resolve traditional charging frustrations. This includes wind-up chargers, zinc-air power packs, USB chargers and multi-tipped universal chargers. These form niche market sectors, but none has met with widespread success.
Our previous applications and provisional applications, including, but not limited to, U.S. patent application Ser. No. 12/018,069, filed Jan. 22, 2008, entitled “Wireless Apparatus and Methods”, the disclosure of which is herewith incorporated by reference, describe wireless transfer of power.
The transmit and receiving antennas are preferably resonant antennas, which are substantially resonant, e.g., within 10% of resonance, 15% of resonance, or 20% of resonance. The antenna is preferably of a small size to allow it to fit into a mobile, handheld device where the available space for the antenna may be limited. An embodiment describes a high efficiency antenna for the specific characteristics and environment for the power being transmitted and received.
One embodiment uses an efficient power transfer between two antennas by storing energy in the near field of the transmitting antenna, rather than sending the energy into free space in the form of a travelling electromagnetic wave. This embodiment increases the quality factor (Q) of the antennas. This can reduce radiation resistance (Rr) and loss resistance (Rl).
In one embodiment, two high-Q antennas are placed such that they react similarly to a loosely coupled transformer, with one antenna inducing power into the other. The antennas preferably have Qs that are greater than 1000.